Everyday Tools
Body Fat % Calculator
Enter your measurements in inches to estimate body fat percentage with the US Navy circumference formula.
Calculation inputs
Measure the waist at the navel, the neck below the larynx, and (for women) the hips at the widest point.
Results
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Complete the fields and select Calculate to show results here.
Estimates only, for general information. Not medical advice.
About this calculator
This tool estimates body fat percentage from a handful of tape-measure circumferences using the US Navy method. It gives people a quick, equipment-free way to track body composition changes over time without a lab test.
How the calculation works
- Men: body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: body fat % = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
- All measurements are in inches
Notes and assumptions
The tape method is an estimate — measurement technique changes the result by a point or two.
It does not distinguish where fat is stored, and very muscular builds can read high.
How it works in plain English
The US Navy method uses height along with neck, waist, and — for women — hip circumference to estimate body fat percentage. Each measurement is taken in inches with a flexible tape: neck just below the larynx, waist at the navel, and hips at their widest point. The formula runs these numbers through logarithms rather than a simple ratio, because body fat does not scale in a straight line with circumference.
For men, the calculation compares waist minus neck against height. For women, waist plus hip minus neck is compared against height. The result is a percentage that places you into a broad category such as athletic, fitness, average, or above average, with separate ranges for men and women because typical fat distribution differs by sex.
Because the formula relies on a handful of tape measurements, small differences in where or how tightly the tape is placed can shift the result by a few points. It works best as a way to track your own trend over weeks or months rather than as a precise one-time reading.
The formula
- Men: body fat % = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450
- Women: body fat % = 495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.22100 x log10(height)) - 450
- All measurements in inches
Worked example
A man is 69 inches tall with a 34-inch waist and a 15-inch neck. Waist minus neck is 19 inches. Plugging height, waist, and neck into the formula gives a denominator of about 1.0324 - 0.19077 x log10(19) + 0.15456 x log10(69), which works out to roughly 0.868. Dividing 495 by that and subtracting 450 gives an estimated body fat of about 20%, which falls in the 'fitness' category for men. A woman of the same height with a 30-inch waist, 40-inch hips, and 13-inch neck would use the waist-plus-hip-minus-neck version of the formula instead.
Commonly cited body fat percentage ranges
| Category | Men | Women |
|---|---|---|
| Essential fat | Under 6% | Under 14% |
| Athletic | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Above average | 25% and up | 32% and up |
Ranges are general classifications widely used for adults and are not diagnostic.
Frequently asked questions
How accurate is the US Navy body fat method?
It is generally accurate to within a few percentage points for most people, which is close enough to track changes over time. It is less reliable for people with unusual body proportions, such as very muscular athletes, whose waist and neck measurements do not follow the typical pattern the formula assumes.
Why does the calculator need a hip measurement for women but not men?
Women tend to store more fat around the hips, so including that measurement improves the estimate's accuracy. Men's fat distribution is more concentrated around the waist, so the male formula relies on waist and neck alone without losing much accuracy.
Where exactly should I measure my waist and neck?
Measure the waist at the navel, keeping the tape level and snug but not compressing the skin. Measure the neck just below the larynx, or Adam's apple, again with the tape level. Consistent placement each time you measure matters more than exact anatomical precision.
Can this replace a DEXA scan or skinfold test?
No. Tape-measure methods are a convenient estimate, not a clinical measurement. DEXA scans and other lab methods directly assess tissue composition and are considerably more precise. This calculator is best used as a free, repeatable way to watch trends between more accurate checkups.
Why did my result change even though I have not lost weight?
Small variations in tape tension, posture, or exact measurement location can shift the reading by a point or two even when your actual body fat has not changed. Try measuring at the same time of day, in the same position, for more consistent comparisons.